Basic TCPClient GET request failing

Troubleshooting
1

Hi all.

Code as follows:

#define REPORT_DOMAIN "my.site.com"
TCPClient client;

void postKey(char* key) 
{

    Serial.print("Attempting to post..:");
    if (client.connect(REPORT_DOMAIN, 80)) {
        Serial.print("Connection OK:");
        client.println("GET http://"+(String)REPORT_DOMAIN+"/r.php?key="+(String)key+" HTTP/1.0");
        client.println("Host: "+(String)REPORT_DOMAIN);
        client.println();
        
        Serial.println("---");
        Serial.println("GET http://"+(String)REPORT_DOMAIN+"/r.php?key="+(String)key+" HTTP/1.0");
        Serial.println("Host: "+(String)REPORT_DOMAIN);
        Serial.println();        
        Serial.println("---");

        uint32_t startWait = micros();
        while(!client.available() && micros() < startWait + 5000) {delayMicroseconds(5);} 
        client.flush();
        client.stop();          
        Serial.print("Posted");
    } else {
        Serial.print("Connection failed..:");
    }
}

When the postKey function is called, I see via the serial debug:

Attempting to post..:Connection OK:---
GET http://my.site.com/r.php?key=TEST HTTP/1.0
Host: my.site..com

---
Posted

However - on the receiving end - nothing shows up.
If I copy / paste the printed data into nc:

[qx.qx-PC] ➤ nc my.site.com 80
GET http://my.site.com/r.php?key=TEST HTTP/1.0
Host: my.site.com
Content-Length: 0

HTTP/1.1 200 OK
Server: nginx

It works.
I’m at a loss at how to further debug this. Anyone had any success with this?
Any update on the webhooks? I thought they were meant to materialise in March :wink:

Thanks kindly.

2

Hi @simon

So get HTTP GET requests work great for me, so I know the core can do it.

Is the key string URL encoded? Could it contain funny characters, not like your TEST example?

What about a Connection: close header?

Or a Content-length: 0 header like in your nc example?

I also send an Accept: text/html, text/plain header.

I think you are using up some memory casting your C strings to Arduino String since I am not sure the compiler is smart enough to do the static analysis here. You can just print your C strings like this:

client.print("Host: ");
client.println(REPORT_DOMAIN);

Also you are only waiting 5ms for the response. That might be OK for a local host on the same subnet, but I know for instance that spark.io is about 140 ms away for me, so might want to try waiting longer.

3

Hi @bko - The test strings were actually just TEST
I will try to implement your suggestions and let you know.

Thank you kindly for your support!

4

And that seemed to do the trick!
It would appear it was the string casts - thanks very much for the suggestion !

2 Likes
5

Hey @bko
Actually, very strange thing:

void postKey(char* key) 
{

    Serial.print("Attempting to post..:");
    if (client.connect(REPORT_DOMAIN, 80)) {
        Serial.print("Connection OK:");
        client.print("GET http://");
        client.print(REPORT_DOMAIN);
        client.print("/r.php?key=");
        client.print(key);
        client.println(" HTTP/1.1");
        client.print("HOST: ");
        client.println(REPORT_DOMAIN);
        client.println("Connection: close");
        client.println();
        
        uint32_t startWait = micros();
        while(!client.available() && micros() < startWait + 5000) {delayMicroseconds(500);} 
        client.flush();
        client.stop();          
        Serial.print("Posted");
    } else {
        Serial.print("Connection failed..:");
    }
}

Fails - but when I change it to (note the LACK of space)

        client.println("HTTP/1.1");

It works. On the receiving end, I get:

array (
  'key' => 'TESTHTTP/1.1:',
)

Which is obviously wrong - but if I add the space in before the HTTP/1.1 - it fails.

This is bang-your-head-on-the-wall type frustrating… any ideas?

6

Hi @simon

You don’t need the “http://” or the host name parts on the GET request. It should look like:

client.print("GET ");
client.print("/r.php?key=");
client.print(key);
client.println(" HTTP/1.1");